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Egle M, Mendez-Carmona N, Segiser A, Graf S, Siepe M, Longnus S. Hypothermic Oxygenated Perfusion Improves Vascular and Contractile Function by Preserving Endothelial Nitric Oxide Production in Cardiac Grafts Obtained With Donation After Circulatory Death. J Am Heart Assoc 2024; 13:e033503. [PMID: 38606732 DOI: 10.1161/jaha.123.033503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2023] [Accepted: 03/01/2024] [Indexed: 04/13/2024]
Abstract
BACKGROUND Cardiac donation after circulatory death is a promising option to increase graft availability. Graft preservation with 30 minutes of hypothermic oxygenated perfusion (HOPE) before normothermic machine perfusion may improve cardiac recovery as compared with cold static storage, the current clinical standard. We investigated the role of preserved nitric oxide synthase activity during HOPE on its beneficial effects. METHODS AND RESULTS Using a rat model of donation after circulatory death, hearts underwent in situ ischemia (21 minutes), were explanted for a cold storage period (30 minutes), and then reperfused under normothermic conditions (60 minutes) with left ventricular loading. Three cold storage conditions were compared: cold static storage, HOPE, and HOPE with Nω-nitro-L-arginine methyl ester (nitric oxide synthase inhibitor). To evaluate potential confounding effects of high coronary flow during early reperfusion in HOPE hearts, bradykinin was administered to normalize coronary flow to HOPE levels in 2 additional groups (cold static storage and HOPE with Nω-nitro-L-arginine methyl ester). Cardiac recovery was significantly improved in HOPE versus cold static storage hearts, as determined by cardiac output, left ventricular work, contraction and relaxation rates, and coronary flow (P<0.05). Furthermore, HOPE attenuated postreperfusion calcium overload. Strikingly, the addition of Nω-nitro-L-arginine methyl ester during HOPE largely abolished its beneficial effects, even when early reperfusion coronary flow was normalized to HOPE levels. CONCLUSIONS HOPE provides superior preservation of ventricular and vascular function compared with the current clinical standard. Importantly, HOPE's beneficial effects require preservation of nitric oxide synthase activity during the cold storage. Therefore, the application of HOPE before normothermic machine perfusion is a promising approach to optimize graft recovery in donation after circulatory death cardiac grafts.
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Affiliation(s)
- Manuel Egle
- Department of Cardiac Surgery Inselspital, Bern University Hospital, University of Bern Switzerland
- Department for BioMedical Research University of Bern Switzerland
- Graduate School for Cellular and Biomedical Sciences University of Bern Switzerland
| | - Natalia Mendez-Carmona
- Department of Cardiac Surgery Inselspital, Bern University Hospital, University of Bern Switzerland
- Department for BioMedical Research University of Bern Switzerland
| | - Adrian Segiser
- Department of Cardiac Surgery Inselspital, Bern University Hospital, University of Bern Switzerland
- Department for BioMedical Research University of Bern Switzerland
| | - Selianne Graf
- Department of Cardiac Surgery Inselspital, Bern University Hospital, University of Bern Switzerland
- Department for BioMedical Research University of Bern Switzerland
- Graduate School for Cellular and Biomedical Sciences University of Bern Switzerland
| | - Matthias Siepe
- Department of Cardiac Surgery Inselspital, Bern University Hospital, University of Bern Switzerland
| | - Sarah Longnus
- Department of Cardiac Surgery Inselspital, Bern University Hospital, University of Bern Switzerland
- Department for BioMedical Research University of Bern Switzerland
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Graf S, Biemmi V, Arnold M, Segiser A, Müller A, Méndez‐Carmona N, Egle M, Siepe M, Barile L, Longnus S. Macrophage-derived extracellular vesicles alter cardiac recovery and metabolism in a rat heart model of donation after circulatory death. J Cell Mol Med 2024; 28:e18281. [PMID: 38652092 PMCID: PMC11037406 DOI: 10.1111/jcmm.18281] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2023] [Revised: 02/11/2024] [Accepted: 03/14/2024] [Indexed: 04/25/2024] Open
Abstract
Conditions to which the cardiac graft is exposed during transplantation with donation after circulatory death (DCD) can trigger the recruitment of macrophages that are either unpolarized (M0) or pro-inflammatory (M1) as well as the release of extracellular vesicles (EV). We aimed to characterize the effects of M0 and M1 macrophage-derived EV administration on post-ischaemic functional recovery and glucose metabolism using an isolated rat heart model of DCD. Isolated rat hearts were subjected to 20 min aerobic perfusion, followed by 27 min global, warm ischaemia or continued aerobic perfusion and 60 min reperfusion with or without intravascular administration of EV. Four experimental groups were compared: (1) no ischaemia, no EV; (2) ischaemia, no EV; (3) ischaemia with M0-macrophage-dervied EV; (4) ischaemia with M1-macrophage-derived EV. Post-ischaemic ventricular and metabolic recovery were evaluated. During reperfusion, ventricular function was decreased in untreated ischaemic and M1-EV hearts, but not in M0-EV hearts, compared to non-ischaemic hearts (p < 0.05). In parallel with the reduced functional recovery in M1-EV versus M0-EV ischaemic hearts, rates of glycolysis from exogenous glucose and oxidative metabolism tended to be lower, while rates of glycogenolysis and lactate release tended to be higher. EV from M0- and M1-macrophages differentially affect post-ischaemic cardiac recovery, potentially by altering glucose metabolism in a rat model of DCD. Targeted EV therapy may be a useful approach for modulating cardiac energy metabolism and optimizing graft quality in the setting of DCD.
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Affiliation(s)
- Selianne Graf
- Department of Cardiac SurgeryInselspital Bern University Hospital, University of BernBernSwitzerland
- Department for BioMedical ResearchUniversity of BernBernSwitzerland
- Graduate School of Cellular and Biomedical SciencesUniversity of BernBernSwitzerland
| | - Vanessa Biemmi
- Laboratory for Cardiovascular TheranosticsCardiocentro Ticino Institute‐EOCLuganoSwitzerland
| | - Maria Arnold
- Department of Cardiac SurgeryInselspital Bern University Hospital, University of BernBernSwitzerland
- Department for BioMedical ResearchUniversity of BernBernSwitzerland
| | - Adrian Segiser
- Department of Cardiac SurgeryInselspital Bern University Hospital, University of BernBernSwitzerland
- Department for BioMedical ResearchUniversity of BernBernSwitzerland
| | - Anja Müller
- Department of Cardiac SurgeryInselspital Bern University Hospital, University of BernBernSwitzerland
- Department for BioMedical ResearchUniversity of BernBernSwitzerland
| | - Natalia Méndez‐Carmona
- Department of Cardiac SurgeryInselspital Bern University Hospital, University of BernBernSwitzerland
- Department for BioMedical ResearchUniversity of BernBernSwitzerland
| | - Manuel Egle
- Department of Cardiac SurgeryInselspital Bern University Hospital, University of BernBernSwitzerland
- Department for BioMedical ResearchUniversity of BernBernSwitzerland
- Graduate School of Cellular and Biomedical SciencesUniversity of BernBernSwitzerland
| | - Matthias Siepe
- Department of Cardiac SurgeryInselspital Bern University Hospital, University of BernBernSwitzerland
| | - Lucio Barile
- Laboratory for Cardiovascular TheranosticsCardiocentro Ticino Institute‐EOCLuganoSwitzerland
| | - Sarah Longnus
- Department of Cardiac SurgeryInselspital Bern University Hospital, University of BernBernSwitzerland
- Department for BioMedical ResearchUniversity of BernBernSwitzerland
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Louradour J, Ottersberg R, Segiser A, Olejnik A, Martínez-Salazar B, Siegrist M, Egle M, Barbieri M, Nimani S, Alerni N, Döring Y, Odening KE, Longnus S. Simultaneous assessment of mechanical and electrical function in Langendorff-perfused ex-vivo mouse hearts. Front Cardiovasc Med 2023; 10:1293032. [PMID: 38028448 PMCID: PMC10663365 DOI: 10.3389/fcvm.2023.1293032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2023] [Accepted: 10/23/2023] [Indexed: 12/01/2023] Open
Abstract
Background The Langendorff-perfused ex-vivo isolated heart model has been extensively used to study cardiac function for many years. However, electrical and mechanical function are often studied separately-despite growing proof of a complex electro-mechanical interaction in cardiac physiology and pathology. Therefore, we developed an isolated mouse heart perfusion system that allows simultaneous recording of electrical and mechanical function. Methods Isolated mouse hearts were mounted on a Langendorff setup and electrical function was assessed via a pseudo-ECG and an octapolar catheter inserted in the right atrium and ventricle. Mechanical function was simultaneously assessed via a balloon inserted into the left ventricle coupled with pressure determination. Hearts were then submitted to an ischemia-reperfusion protocol. Results At baseline, heart rate, PR and QT intervals, intra-atrial and intra-ventricular conduction times, as well as ventricular effective refractory period, could be measured as parameters of cardiac electrical function. Left ventricular developed pressure (DP), left ventricular work (DP-heart rate product) and maximal velocities of contraction and relaxation were used to assess cardiac mechanical function. Cardiac arrhythmias were observed with episodes of bigeminy during which DP was significantly increased compared to that of sinus rhythm episodes. In addition, the extrasystole-triggered contraction was only 50% of that of sinus rhythm, recapitulating the "pulse deficit" phenomenon observed in bigeminy patients. After ischemia, the mechanical function significantly decreased and slowly recovered during reperfusion while most of the electrical parameters remained unchanged. Finally, the same electro-mechanical interaction during episodes of bigeminy at baseline was observed during reperfusion. Conclusion Our modified Langendorff setup allows simultaneous recording of electrical and mechanical function on a beat-to-beat scale and can be used to study electro-mechanical interaction in isolated mouse hearts.
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Affiliation(s)
- Julien Louradour
- Department of Physiology, Translational Cardiology/Electrophysiology, Institute of Physiology, University of Bern, Bern, Switzerland
| | - Rahel Ottersberg
- Department for BioMedical Research, University of Bern, Bern, Switzerland
- Department of Cardiac Surgery, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Adrian Segiser
- Department for BioMedical Research, University of Bern, Bern, Switzerland
- Department of Cardiac Surgery, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Agnieszka Olejnik
- Department for BioMedical Research, University of Bern, Bern, Switzerland
- Division of Clinical Chemistry and Laboratory Hematology, Department of Medical Laboratory Diagnostics, Faculty of Pharmacy, Wroclaw Medical University, Wroclaw, Poland
| | - Berenice Martínez-Salazar
- Department for BioMedical Research, University of Bern, Bern, Switzerland
- Department of Angiology, Swiss Cardiovascular Center, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Mark Siegrist
- Department for BioMedical Research, University of Bern, Bern, Switzerland
- Department of Angiology, Swiss Cardiovascular Center, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Manuel Egle
- Department for BioMedical Research, University of Bern, Bern, Switzerland
- Department of Cardiac Surgery, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Miriam Barbieri
- Department of Physiology, Translational Cardiology/Electrophysiology, Institute of Physiology, University of Bern, Bern, Switzerland
| | - Saranda Nimani
- Department of Physiology, Translational Cardiology/Electrophysiology, Institute of Physiology, University of Bern, Bern, Switzerland
| | - Nicolò Alerni
- Department of Physiology, Translational Cardiology/Electrophysiology, Institute of Physiology, University of Bern, Bern, Switzerland
| | - Yvonne Döring
- Department for BioMedical Research, University of Bern, Bern, Switzerland
- Department of Angiology, Swiss Cardiovascular Center, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Institute for Cardiovascular Prevention (IPEK), Ludwig-Maximilians-University Munich (LMU), Munich, Germany
- German Center for Cardiovascular Research (DZHK), Partner Site Munich, Heart Alliance Munich, Munich, Germany
| | - Katja E. Odening
- Department of Physiology, Translational Cardiology/Electrophysiology, Institute of Physiology, University of Bern, Bern, Switzerland
- Department of Cardiology, Translational Cardiology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Sarah Longnus
- Department for BioMedical Research, University of Bern, Bern, Switzerland
- Department of Cardiac Surgery, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
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Clavier A, Arnold M, Segiser A, Mendez-Carmona N, Wyss R, Uldry A, Heller M, Siepe M, Longnus S. Proteins Released During Ex-Vivo Perfusion are Promising Biomarkers for Cardiac Graft Quality: Studies in an Isolated Rat Heart Model of DCD. J Heart Lung Transplant 2023. [DOI: 10.1016/j.healun.2023.02.1549] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/05/2023] Open
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5
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Egle M, Graf S, Segiser A, Sanz M, Clavier A, Arnold M, Kadner A, Carrel T, Siepe M, Longnus S. Functional Assessment During Unloaded, Ex-Vivo Perfusion Could Help Predict Recovery in Cardiac Dcd Grafts: Studies in a Porcine Model. J Heart Lung Transplant 2023. [DOI: 10.1016/j.healun.2023.02.880] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/05/2023] Open
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6
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Graf S, Egle M, Sanz M, Segiser A, Arnold M, Kadner A, Siepe M, Longnus S. Circulating Factors, Measured Both in the Donor and During Ex-Vivo Heart Perfusion, Correlate with Subsequent Heart Recovery in a Pig Model of Dcd. J Heart Lung Transplant 2023. [DOI: 10.1016/j.healun.2023.02.1096] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/05/2023] Open
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Méndez-Carmona N, Wyss RK, Arnold M, Segiser A, Kalbermatter N, Joachimbauer A, Carrel TP, Longnus SL. Effects of graft preservation conditions on coronary endothelium and cardiac functional recovery in a rat model of donation after circulatory death. J Heart Lung Transplant 2021; 40:1396-1407. [PMID: 34509349 DOI: 10.1016/j.healun.2021.07.028] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Revised: 07/15/2021] [Accepted: 07/26/2021] [Indexed: 01/15/2023] Open
Abstract
BACKGROUND Use of cardiac grafts obtained with donation after circulatory death (DCD) could significantly improve donor heart availability. As DCD hearts undergo potentially deleterious warm ischemia and reperfusion, clinical protocols require optimization to ensure graft quality. Thus, we investigated effects of alternative preservation conditions on endothelial and/or vascular and contractile function in comparison with the current clinical standard. METHODS Using a rat DCD model, we compared currently used graft preservation conditions, St. Thomas n°2 (St. T) at 4°C, with potentially more suitable conditions for DCD hearts, adenosine-lidocaine preservation solution (A-L) at 4°C or 22°C. Following general anesthesia and diaphragm transection, hearts underwent either 0 or 18 min of in-situ warm ischemia, were explanted, flushed and stored for 15 min with either St. T at 4°C or A-L at 4°C or 22°C, and then reperfused under normothermic, aerobic conditions. Endothelial integrity and contractile function were determined. RESULTS Compared to 4°C preservation, 22°C A-L significantly increased endothelial nitric oxide synthase (eNOS) dimerization and reduced oxidative tissue damage (p < 0.05 for all). Furthermore, A-L at 22°C better preserved the endothelial glycocalyx and coronary flow compared with St. T, tended to reduce tissue calcium overload, and stimulated pro-survival signaling. No significant differences were observed in cardiac function among ischemic groups. CONCLUSIONS Twenty-two-degree Celsius A-L solution better preserves the coronary endothelium compared to 4°C St. T, which likely results from greater eNOS dimerization, reduced oxidative stress, and activation of the reperfusion injury salvage kinase (RISK) pathway. Improving heart preservation conditions immediately following warm ischemia constitutes a promising approach for the optimization of clinical protocols in DCD heart transplantation.
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Affiliation(s)
- Natalia Méndez-Carmona
- Department of Cardiovascular Surgery, Inselspital, Bern University Hospital and Department for BioMedical Research (DBMR), University of Bern, Bern, Switzerland
| | - Rahel K Wyss
- Department of Cardiovascular Surgery, Inselspital, Bern University Hospital and Department for BioMedical Research (DBMR), University of Bern, Bern, Switzerland
| | - Maria Arnold
- Department of Cardiovascular Surgery, Inselspital, Bern University Hospital and Department for BioMedical Research (DBMR), University of Bern, Bern, Switzerland
| | - Adrian Segiser
- Department of Cardiovascular Surgery, Inselspital, Bern University Hospital and Department for BioMedical Research (DBMR), University of Bern, Bern, Switzerland
| | - Nina Kalbermatter
- Department of Cardiovascular Surgery, Inselspital, Bern University Hospital and Department for BioMedical Research (DBMR), University of Bern, Bern, Switzerland
| | - Anna Joachimbauer
- Department of Cardiovascular Surgery, Inselspital, Bern University Hospital and Department for BioMedical Research (DBMR), University of Bern, Bern, Switzerland
| | - Thierry P Carrel
- Department of Cardiovascular Surgery, Inselspital, Bern University Hospital and Department for BioMedical Research (DBMR), University of Bern, Bern, Switzerland
| | - Sarah L Longnus
- Department of Cardiovascular Surgery, Inselspital, Bern University Hospital and Department for BioMedical Research (DBMR), University of Bern, Bern, Switzerland.
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Arnold M, Segiser A, Graf S, Méndez-Carmona N, Sanz MN, Wyss RK, Kalbermatter N, Keller N, Carrel T, Longnus S. Pre-ischemic Lactate Levels Affect Post-ischemic Recovery in an Isolated Rat Heart Model of Donation After Circulatory Death (DCD). Front Cardiovasc Med 2021; 8:669205. [PMID: 34195235 PMCID: PMC8236508 DOI: 10.3389/fcvm.2021.669205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Accepted: 05/12/2021] [Indexed: 11/23/2022] Open
Abstract
Introduction: Donation after circulatory death (DCD) could substantially improve donor heart availability. In DCD, the heart is not only exposed to a period of warm ischemia, but also to a damaging pre-ischemic phase. We hypothesized that the DCD-relevant pre-ischemic lactate levels negatively affect the post-ischemic functional and mitochondrial recovery in an isolated rat heart model of DCD. Methods: Isolated, working rat hearts underwent 28.5′ of global ischemia and 60′ of reperfusion. Prior to ischemia, hearts were perfused with one of three pre-ischemic lactate levels: no lactate (0 Lac), physiologic lactate (0.5 mM; 0.5 Lac), or DCD-relevant lactate (1 mM; 1 Lac). In a fourth group, an inhibitor of the mitochondrial calcium uniporter was added in reperfusion to 1 Lac hearts (1 Lac + Ru360). Results: During reperfusion, left ventricular work (heart rate-developed pressure product) was significantly greater in 0.5 Lac hearts compared to 0 Lac or 1 Lac. In 1 vs. 0.5 Lac hearts, in parallel with a decreased function, cellular and mitochondrial damage was greater, tissue calcium content tended to increase, while oxidative stress damage tended to decrease. The addition of Ru360 to 1 Lac hearts partially abrogated the negative effects of the DCD-relevant pre-ischemic lactate levels (greater post-ischemic left ventricular work and less cytochrome c release in 1 Lac+Ru360 vs. 1 Lac). Conclusion: DCD-relevant levels of pre-ischemic lactate (1 mM) reduce contractile, cellular, and mitochondrial recovery during reperfusion compared to physiologic lactate levels. Inhibition of mitochondrial calcium uptake during early reperfusion improves the post-ischemic recovery of 1 Lac hearts, indicating calcium overload as a potential therapeutic reperfusion target for DCD hearts.
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Affiliation(s)
- Maria Arnold
- Department of Cardiovascular Surgery, Inselspital, Bern University Hospital, Bern, Switzerland.,Department for BioMedical Research, University of Bern, Bern, Switzerland
| | - Adrian Segiser
- Department of Cardiovascular Surgery, Inselspital, Bern University Hospital, Bern, Switzerland.,Department for BioMedical Research, University of Bern, Bern, Switzerland
| | - Selianne Graf
- Department of Cardiovascular Surgery, Inselspital, Bern University Hospital, Bern, Switzerland.,Department for BioMedical Research, University of Bern, Bern, Switzerland
| | - Natalia Méndez-Carmona
- Department of Cardiovascular Surgery, Inselspital, Bern University Hospital, Bern, Switzerland.,Department for BioMedical Research, University of Bern, Bern, Switzerland
| | - Maria N Sanz
- Department of Cardiovascular Surgery, Inselspital, Bern University Hospital, Bern, Switzerland.,Department for BioMedical Research, University of Bern, Bern, Switzerland
| | - Rahel K Wyss
- Department of Cardiovascular Surgery, Inselspital, Bern University Hospital, Bern, Switzerland.,Department for BioMedical Research, University of Bern, Bern, Switzerland
| | - Nina Kalbermatter
- Department of Cardiovascular Surgery, Inselspital, Bern University Hospital, Bern, Switzerland.,Department for BioMedical Research, University of Bern, Bern, Switzerland
| | - Nino Keller
- Department of Cardiovascular Surgery, Inselspital, Bern University Hospital, Bern, Switzerland.,Department for BioMedical Research, University of Bern, Bern, Switzerland
| | - Thierry Carrel
- Department of Cardiovascular Surgery, Inselspital, Bern University Hospital, Bern, Switzerland.,Department for BioMedical Research, University of Bern, Bern, Switzerland
| | - Sarah Longnus
- Department of Cardiovascular Surgery, Inselspital, Bern University Hospital, Bern, Switzerland.,Department for BioMedical Research, University of Bern, Bern, Switzerland
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9
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Guensch DP, Michel MC, Huettenmoser SP, Jung B, Gulac P, Segiser A, Longnus SL, Fischer K. The blood oxygen level dependent (BOLD) effect of in-vitro myoglobin and hemoglobin. Sci Rep 2021; 11:11464. [PMID: 34075096 PMCID: PMC8169704 DOI: 10.1038/s41598-021-90908-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2020] [Accepted: 05/18/2021] [Indexed: 01/23/2023] Open
Abstract
The presence of deoxygenated hemoglobin (Hb) results in a drop in T2 and T2* in magnetic resonance imaging (MRI), known as the blood oxygenation level-dependent (BOLD-)effect. The purpose of this study was to investigate if deoxygenated myoglobin (Mb) exerts a BOLD-like effect. Equine Met-Mb powder was dissolved and converted to oxygenated Mb. T1, T2, T2*-maps and BOLD-bSSFP images at 3Tesla were used to scan 22 Mb samples and 12 Hb samples at room air, deoxygenation, reoxygenation and after chemical reduction. In Mb, T2 and T2* mapping showed a significant decrease after deoxygenation (- 25% and - 12%, p < 0.01), increase after subsequent reoxygenation (+ 17% and 0% vs. room air, p < 0.01), and finally a decrease in T2 after chemical reduction (- 28%, p < 0.01). An opposite trend was observed with T1 for each stage, while chemical reduction reduced BOLD-bSSFP signal (- 3%, p < 0.01). Similar deflections were seen at oxygenation changes in Hb. The T1 changes suggests that the oxygen content has been changed in the specimen. The shortening of transverse relaxation times in T2 and T2*-mapping after deoxygenation in Mb specimens are highly indicative of a BOLD-like effect.
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Affiliation(s)
- Dominik P Guensch
- Department of Anaesthesiology and Pain Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland. .,Department of Diagnostic, Interventional and Paediatric Radiology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland.
| | - Matthias C Michel
- Department of Anaesthesiology and Pain Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Stefan P Huettenmoser
- Department of Diagnostic, Interventional and Paediatric Radiology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Bernd Jung
- Department of Diagnostic, Interventional and Paediatric Radiology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Patrik Gulac
- Department of Cardiovascular Surgery, Inselspital, Bern University Hospital, University of Bern , Bern, Switzerland.,Department for BioMedical Research, University of Bern, Bern, Switzerland.,Department of Pharmacology and Toxicology, Faculty of Pharmacy, Comenius University, Bratislava, Slovakia
| | - Adrian Segiser
- Department of Cardiovascular Surgery, Inselspital, Bern University Hospital, University of Bern , Bern, Switzerland.,Department for BioMedical Research, University of Bern, Bern, Switzerland
| | - Sarah L Longnus
- Department of Cardiovascular Surgery, Inselspital, Bern University Hospital, University of Bern , Bern, Switzerland.,Department for BioMedical Research, University of Bern, Bern, Switzerland
| | - Kady Fischer
- Department of Anaesthesiology and Pain Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
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Egle M, Mendez-Carmona N, Arnold M, Segiser A, Carrel T, Longnus S. Effects of Hope (Hypothermic Oxygenated Perfusion) on Preservation of Vascular and Contractile Function in Cardiac Grafts in a Rat Model of Donation after Circulatory Death (DCD). J Heart Lung Transplant 2021. [DOI: 10.1016/j.healun.2021.01.677] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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11
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Graf S, Arnold M, Segiser A, Méndez-Carmona N, Kalbermatter N, Carrel T, Longnus S. Pre-Ischemic Lactate Levels Affect Post-Ischemic Functional Recovery in an Isolated Rat Heart Model of Donation after Circulatory Death (DCD). J Heart Lung Transplant 2021. [DOI: 10.1016/j.healun.2021.01.678] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
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12
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Wyss RK, Méndez Carmona N, Arnold M, Segiser A, Mueller M, Dutkowski P, Carrel TP, Longnus SL. Hypothermic, oxygenated perfusion (HOPE) provides cardioprotection via succinate oxidation prior to normothermic perfusion in a rat model of donation after circulatory death (DCD). Am J Transplant 2021; 21:1003-1011. [PMID: 32786170 DOI: 10.1111/ajt.16258] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Revised: 07/29/2020] [Accepted: 07/30/2020] [Indexed: 01/25/2023]
Abstract
In donation after circulatory death (DCD), cardiac grafts are subjected to warm ischemia in situ, prior to a brief period of cold, static storage (CSS) at procurement, and ex situ, normothermic, machine perfusion (NMP) for transport and graft evaluation. Cold ischemia and normothermic reoxygenation during NMP could aggravate graft injury through continued accumulation and oxidation, respectively, of mitochondrial succinate, and the resultant oxidative stress. We hypothesized that replacing CSS with hypothermic, oxygenated perfusion (HOPE) could provide cardioprotection by reducing cardiac succinate levels before NMP. DCD was simulated in male Wistar rats. Following 21 minutes in situ ischemia, explanted hearts underwent 30 minutes hypothermic storage with 1 of the following: (1) CSS, (2) HOPE, (3) hypothermic deoxygenated perfusion (HNPE), or (4) HOPE + AA5 (succinate dehydrogenase inhibitor) followed by normothermic reperfusion to measure cardiac and metabolic recovery. After hypothermic storage, tissue ATP/ADP levels were higher and succinate concentration was lower in HOPE vs CSS, HNPE, and HOPE + AA5 hearts. After 60 minutes reperfusion, cardiac function was increased and cellular injury was decreased in HOPE compared with CSS, HNPE, and HOPE + AA5 hearts. HOPE provides improved cardioprotection via succinate oxidation prior to normothermic reperfusion compared with CSS, and therefore is a promising strategy for preservation of cardiac grafts obtained with DCD.
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Affiliation(s)
- Rahel K Wyss
- Department of Cardiovascular Surgery, Inselspital, University Hospital Bern, Bern, Switzerland.,Department for BioMedical Research, University of Bern, Bern, Switzerland
| | - Natalia Méndez Carmona
- Department of Cardiovascular Surgery, Inselspital, University Hospital Bern, Bern, Switzerland.,Department for BioMedical Research, University of Bern, Bern, Switzerland
| | - Maria Arnold
- Department of Cardiovascular Surgery, Inselspital, University Hospital Bern, Bern, Switzerland.,Department for BioMedical Research, University of Bern, Bern, Switzerland
| | - Adrian Segiser
- Department of Cardiovascular Surgery, Inselspital, University Hospital Bern, Bern, Switzerland.,Department for BioMedical Research, University of Bern, Bern, Switzerland
| | - Matteo Mueller
- Department of Surgery and Transplantation, University Hospital Zurich, Zurich, Switzerland
| | - Philipp Dutkowski
- Department of Surgery and Transplantation, University Hospital Zurich, Zurich, Switzerland
| | - Thierry P Carrel
- Department of Cardiovascular Surgery, Inselspital, University Hospital Bern, Bern, Switzerland.,Department for BioMedical Research, University of Bern, Bern, Switzerland
| | - Sarah L Longnus
- Department of Cardiovascular Surgery, Inselspital, University Hospital Bern, Bern, Switzerland.,Department for BioMedical Research, University of Bern, Bern, Switzerland
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Wyss RK, Méndez-Carmona N, Sanz MN, Arnold M, Segiser A, Fiedler GM, Carrel TP, Djafarzadeh S, Tevaearai Stahel HT, Longnus SL. Mitochondrial integrity during early reperfusion in an isolated rat heart model of donation after circulatory death-consequences of ischemic duration. J Heart Lung Transplant 2018; 38:647-657. [PMID: 30655178 DOI: 10.1016/j.healun.2018.12.013] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Revised: 11/13/2018] [Accepted: 12/18/2018] [Indexed: 12/27/2022] Open
Abstract
BACKGROUND Cardioprotection and graft evaluation after ischemia-reperfusion (IR) are essential in facilitating heart transplantation with donation after circulatory death. Given the key role of mitochondria in IR, we aimed to investigate the tolerance of cardiac mitochondria to warm, global ischemia and to determine the predictive value of early reperfusion mitochondria-related parameters for post-ischemic cardiac recovery. METHODS Isolated, working rat hearts underwent 0, 21, 24, 27, 30, or 33 minutes of warm, global ischemia, followed by 60 minutes of reperfusion. Functional recovery (developed pressure × heart rate) was determined at 60 minutes of reperfusion, whereas mitochondrial integrity was measured at 10 minutes of reperfusion. RESULTS Functional recovery at 60 minutes of reperfusion decreased with ≥ 27 minutes of ischemia vs no ischemia (n = 7-8/group; p < 0.01). Cytochrome c, succinate release, and mitochondrial Ca2+ content increased with ≥ 27 minutes of ischemia vs no ischemia (p < 0.05). Ischemia at ≥ 21 minutes decreased mitochondrial coupling, adenosine 5'-triphosphate content, mitochondrial Ca2+ retention capacity, and increased oxidative damage vs no ischemia (p < 0.05). Reactive oxygen species (ROS) from reverse electron transfer increased with 21 and 27 minutes of ischemia vs no ischemia and 33 minutes of ischemia (p < 0.05), whereas ROS from forward electron transfer increased only with 33 minutes of ischemia vs no ischemia (p < 0.05). Mitochondrial coupling and adenosine 5'-triphosphate content correlated positively and cytochrome c, succinate, oxidative damage, and mitochondrial Ca2+ content correlated negatively with cardiac functional recovery (p < 0.05). CONCLUSIONS Mitochondrial dysfunction occurs with shorter periods of ischemia than cardiac dysfunction. Mitochondrial coupling, ROS emission from reverse electron transfer, and calcium retention are particularly sensitive to early reperfusion injury, reflecting potential targets for cardioprotection. Indicators of mitochondrial integrity may be of aid in evaluating suitability of donation after circulatory death grafts for transplantation.
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Affiliation(s)
- Rahel K Wyss
- Department of Cardiovascular Surgery, Inselspital, University Hospital Bern, Bern, Switzerland; Department for BioMedical Research, University of Bern, Bern, Switzerland
| | - Natalia Méndez-Carmona
- Department of Cardiovascular Surgery, Inselspital, University Hospital Bern, Bern, Switzerland; Department for BioMedical Research, University of Bern, Bern, Switzerland
| | - Maria-Nieves Sanz
- Department of Cardiovascular Surgery, Inselspital, University Hospital Bern, Bern, Switzerland; Department for BioMedical Research, University of Bern, Bern, Switzerland
| | - Maria Arnold
- Department of Cardiovascular Surgery, Inselspital, University Hospital Bern, Bern, Switzerland; Department for BioMedical Research, University of Bern, Bern, Switzerland
| | - Adrian Segiser
- Department of Cardiovascular Surgery, Inselspital, University Hospital Bern, Bern, Switzerland; Department for BioMedical Research, University of Bern, Bern, Switzerland
| | - Georg M Fiedler
- Center of Laboratory Medicine, University Institute of Clinical Chemistry, Bern, Switzerland
| | - Thierry P Carrel
- Department of Cardiovascular Surgery, Inselspital, University Hospital Bern, Bern, Switzerland; Department for BioMedical Research, University of Bern, Bern, Switzerland
| | - Siamak Djafarzadeh
- Department for BioMedical Research, University of Bern, Bern, Switzerland; Department of Intensive Care Medicine, Inselspital, University Hospital Bern, Bern, Switzerland
| | - Hendrik T Tevaearai Stahel
- Department of Cardiovascular Surgery, Inselspital, University Hospital Bern, Bern, Switzerland; Department for BioMedical Research, University of Bern, Bern, Switzerland.
| | - Sarah L Longnus
- Department of Cardiovascular Surgery, Inselspital, University Hospital Bern, Bern, Switzerland; Department for BioMedical Research, University of Bern, Bern, Switzerland
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Jungi S, Fu X, Segiser A, Busch M, Most P, Fiedler M, Carrel T, Tevaearai Stahel H, Longnus SL, Most H. Enhanced Cardiac S100A1 Expression Improves Recovery from Global Ischemia-Reperfusion Injury. J Cardiovasc Transl Res 2018; 11:236-245. [PMID: 29392537 DOI: 10.1007/s12265-018-9788-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Accepted: 01/08/2018] [Indexed: 12/14/2022]
Abstract
Gene-targeted therapy with the inotropic Ca2 + -sensor protein S100A1 rescues contractile function in post-ischemic heart failure and is being developed towards clinical trials. Its proven beneficial effect on cardiac metabolism and mitochondrial function suggests a cardioprotective effect of S100A1 in myocardial ischemia-reperfusion injury (IRI). Fivefold cardiomyocyte-specific S100A1 overexpressing, isolated rat hearts perfused in working mode were subjected to 28 min ischemia (37 °C) followed by 60 min reperfusion. S100A1 overexpressing hearts showed superior hemodynamic recover: Left ventricular pressure recovered to 57 ± 7.3% of baseline compared to 51 ± 4.6% in control (p = 0.025), this effect mirrored in LV work and dP/dt(max). Troponin T and lactate dehydrogenase was decreased in the S100A1 group, as well as FoxO pro-apoptotic transcription factor, indicating less tissue necrosis, whereas phosphocreatine content was higher after reperfusion. This is the first report of a cardioprotective effect of S100A1 overexpression in a global IRI model.
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Affiliation(s)
- S Jungi
- Department of Cardiovascular Surgery, Inselspital University Hospital, University of Bern, 3010, Bern, Switzerland
| | - X Fu
- Department of Cardiovascular Surgery, Inselspital University Hospital, University of Bern, 3010, Bern, Switzerland
| | - A Segiser
- Department of Cardiovascular Surgery, Inselspital University Hospital, University of Bern, 3010, Bern, Switzerland
| | - M Busch
- Section for Molecular and Translational Cardiology, Department of Cardiology, Pneumology and Angiology, Karl-Ruprechts University of Heidelberg, Heidelberg, Germany.,German Center for Cardiovascular Research (DZHK), Partner Site Heidelberg/Mannheim, Heidelberg, Germany
| | - P Most
- Section for Molecular and Translational Cardiology, Department of Cardiology, Pneumology and Angiology, Karl-Ruprechts University of Heidelberg, Heidelberg, Germany.,German Center for Cardiovascular Research (DZHK), Partner Site Heidelberg/Mannheim, Heidelberg, Germany
| | - M Fiedler
- Center for Laboratory Medicine, Inselspital University Hospital, University of Bern, Bern, Switzerland
| | - T Carrel
- Department of Cardiovascular Surgery, Inselspital University Hospital, University of Bern, 3010, Bern, Switzerland
| | - H Tevaearai Stahel
- Department of Cardiovascular Surgery, Inselspital University Hospital, University of Bern, 3010, Bern, Switzerland
| | - S L Longnus
- Department of Cardiovascular Surgery, Inselspital University Hospital, University of Bern, 3010, Bern, Switzerland
| | - Henriette Most
- Department of Cardiovascular Surgery, Inselspital University Hospital, University of Bern, 3010, Bern, Switzerland.
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Zuppinger C, Gibbons G, Dutta-Passecker P, Segiser A, Most H, Suter TM. Characterization of cytoskeleton features and maturation status of cultured human iPSC-derived cardiomyocytes. Eur J Histochem 2017; 61:2763. [PMID: 28735524 PMCID: PMC5484009 DOI: 10.4081/ejh.2017.2763] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 06/07/2017] [Accepted: 06/07/2017] [Indexed: 01/01/2023] Open
Abstract
Recent innovations in stem cell technologies and the availability of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) have opened new possibilities for studies and drug testing on human cardiomyocytes in vitro. Still, there are concerns about the precise nature of such 'reprogrammed' cells. We have performed an investigation using immunocytochemistry and confocal microscopy on several cellular features using commercially available hiPSC-CMs. For some selected developmentally regulated or cardiac chamber-specific proteins, we have compared the results from hiPSC-derived cardiomyocytes with freshly isolated, ventricular cardiomyocytes from adult rats. The results show that all typical cardiac proteins are expressed in these hiPSC-CMs. Furthermore, intercalated disc-like structures, calcium cycling proteins, and myofibrils are present. However, some of these proteins are only known from early developmental stages of the ventricular myocardium or the diseased adult heart. A heterogeneous expression pattern in the cell population was noted for some muscle proteins, such as for myosin light chains, or incomplete organization in sarcomeres, such as for telethonin. These observations indicate that hiPSC-CMs can be considered genuine human cardiomyocytes of an early developmental state. The here described marker proteins of maturation may become instrumental in future studies attempting the improvement of cardiomyocyte in vitro models.
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Fu X, Segiser A, Carrel TP, Tevaearai Stahel HT, Most H. Rat Heterotopic Heart Transplantation Model to Investigate Unloading-Induced Myocardial Remodeling. Front Cardiovasc Med 2016; 3:34. [PMID: 27807535 PMCID: PMC5069686 DOI: 10.3389/fcvm.2016.00034] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2016] [Accepted: 09/20/2016] [Indexed: 12/17/2022] Open
Abstract
Unloading of the failing left ventricle in order to achieve myocardial reverse remodeling and improvement of contractile function has been developed as a strategy with the increasing frequency of implantation of left ventricular assist devices in clinical practice. But, reverse remodeling remains an elusive target, with high variability and exact mechanisms still largely unclear. The small animal model of heterotopic heart transplantation (hHTX) in rodents has been widely implemented to study the effects of complete and partial unloading on cardiac failing and non-failing tissue to better understand the structural and molecular changes that underlie myocardial recovery. We herein review the current knowledge on the effects of volume unloading the left ventricle via different methods of hHTX in rats, differentiating between changes that contribute to functional recovery and adverse effects observed in unloaded myocardium. We focus on methodological aspects of heterotopic transplantation, which increase the correlation between the animal model and the setting of the failing unloaded human heart. Last, but not least, we describe the late use of sophisticated techniques to acquire data, such as small animal MRI and catheterization, as well as ways to assess unloaded hearts under "reloaded" conditions. While giving regard to certain limitations, heterotopic rat heart transplantation certainly represents the crucial model to mimic unloading-induced changes in the heart and as such the intricacies and challenges deserve highest consideration. Careful translational research will further improve our knowledge of the reverse remodeling process and how to potentiate its effect in order to achieve recovery of contractile function in more patients.
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Affiliation(s)
- Xuebin Fu
- Department of Cardiac and Vascular Surgery, Inselspital University Hospital , Berne , Switzerland
| | - Adrian Segiser
- Department of Cardiac and Vascular Surgery, Inselspital University Hospital , Berne , Switzerland
| | - Thierry P Carrel
- Department of Cardiac and Vascular Surgery, Inselspital University Hospital , Berne , Switzerland
| | | | - Henriette Most
- Department of Cardiac and Vascular Surgery, Inselspital University Hospital , Berne , Switzerland
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17
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Most H, Segiser A, Fu X, Zuppinger C, Ullrich ND, Longnus SL, Carrel TP, Tevaearai HT. P682Preserved contractile function of unloaded cardiomyocytes despite diminished sarcomere size is associated with troponin I activation. Cardiovasc Res 2014. [DOI: 10.1093/cvr/cvu098.106] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Brinks H, Giraud MN, Segiser A, Ferrié C, Longnus S, Ullrich ND, Koch WJ, Most P, Carrel TP, Tevaearai HT. Dynamic patterns of ventricular remodeling and apoptosis in hearts unloaded by heterotopic transplantation. J Heart Lung Transplant 2013; 33:203-10. [PMID: 24315785 DOI: 10.1016/j.healun.2013.10.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2013] [Revised: 09/22/2013] [Accepted: 10/01/2013] [Indexed: 01/20/2023] Open
Abstract
BACKGROUND Mechanical unloading of failing hearts can trigger functional recovery but results in progressive atrophy and possibly detrimental adaptation. In an unbiased approach, we examined the dynamic effects of unloading duration on molecular markers indicative of myocardial damage, hypothesizing that potential recovery may be improved by optimized unloading time. METHODS Heterotopically transplanted normal rat hearts were harvested at 3, 8, 15, 30, and 60 days. Forty-seven genes were analyzed using TaqMan-based microarray, Western blot, and immunohistochemistry. RESULTS In parallel with marked atrophy (22% to 64% volume loss at 3 respectively 60 days), expression of myosin heavy-chain isoforms (MHC-α/-β) was characteristically switched in a time-dependent manner. Genes involved in tissue remodeling (FGF-2, CTGF, TGFb, IGF-1) were increasingly upregulated with duration of unloading. A distinct pattern was observed for genes involved in generation of contractile force; an indiscriminate early downregulation was followed by a new steady-state below normal. For pro-apoptotic transcripts bax, bnip-3, and cCasp-6 and -9 mRNA levels demonstrated a slight increase up to 30 days unloading with pronunciation at 60 days. Findings regarding cell death were confirmed on the protein level. Proteasome activity indicated early increase of protein degradation but decreased below baseline in unloaded hearts at 60 days. CONCLUSIONS We identified incrementally increased apoptosis after myocardial unloading of the normal rat heart, which is exacerbated at late time points (60 days) and inversely related to loss of myocardial mass. Our findings suggest an irreversible detrimental effect of long-term unloading on myocardium that may be precluded by partial reloading and amenable to molecular therapeutic intervention.
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Affiliation(s)
- Henriette Brinks
- Department of Cardiac and Vascular Surgery, Inselspital University Hospital, Berne, Switzerland.
| | - Marie-Noelle Giraud
- Cardiology, Department of Medicine, University of Fribourg, Fribourg, Switzerland
| | - Adrian Segiser
- Department of Cardiac and Vascular Surgery, Inselspital University Hospital, Berne, Switzerland
| | - Celine Ferrié
- Department of Cardiac and Vascular Surgery, Inselspital University Hospital, Berne, Switzerland
| | - Sarah Longnus
- Department of Cardiac and Vascular Surgery, Inselspital University Hospital, Berne, Switzerland
| | - Nina D Ullrich
- Institute of Physiology, University of Berne, Berne, Switzerland
| | - Walter J Koch
- Center for Translational Medicine, Department of Pharmacology, Temple University, Philadelphia, Pennsylvania
| | - Patrick Most
- Center for Molecular and Translational Cardiology, Department of Internal Medicine III, University of Heidelberg, Germany
| | - Thierry P Carrel
- Department of Cardiac and Vascular Surgery, Inselspital University Hospital, Berne, Switzerland
| | - Hendrik T Tevaearai
- Department of Cardiac and Vascular Surgery, Inselspital University Hospital, Berne, Switzerland
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